Instinct and Discernment 



that we shall have come as near to the truth 

 as the state of our knowledge will allow for 

 the moment. 



Having thus assigned a due share both 

 to instinct and to its aberrations when the 

 course of its different phases is disturbed, 

 let us see what discernment is able to do 

 in the selection of a site for the nest and 

 materials for building it; and, leaving the 

 Pelopaeus, upon whom it is useles to dwell 

 any longer, let us consider other examples, 

 picked from among those richest in varia- 

 tions. 



The Mason-bee of the Sheds (Chali- 

 codoma rufitarsis, Perez) well deserves the 

 name which I have felt justified in giving 

 her from her habits: she settles in numerous 

 colonies in our sheds, on the lower surface 

 of the tiles, where she builds huge nests 

 which endanger the solidity of the roof. 

 Nowhere does the insect display a greater 

 zeal for work than in one of these colossal 

 cities, an estate which is constantly increas- 

 ing as it passes down from one generation 

 to another; nowhere does it find a better 

 workshop for the exercise of its industry. 

 Here it has plenty of room, a quiet resting- 

 place, sheltered from damp and from ex- 

 cess of heat or cold. 



163 



